An Observation on Tensile Fracture of Wood by Scanning Electron Microscope Hiroshi SAIKI, Ikuo FURUKAWA and Hiroshi HARADA

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(1972), 43: 309- Issue Date 1972-03-15 URL http://hdl.handle.

1 Title 木材の縦引張破断面の走査電子顕微鏡による観察 Author(s) 佐伯, 浩 ; 古川, 郁夫 ; 原田, 浩 Citation 京都大学農学部演習林報告 = BULLETIN OF THE KYOT UNIVERSITY FORESTS (1972), 43: 309- Issue Date URL Right Type Departmental Bulletin Paper Textversion publisher Kyoto University

2 An Observation on Tensile Fracture of Wood by Scanning Electron Microscope Hiroshi SAIKI, Ikuo FURUKAWA and Hiroshi HARADA

Résumé Wood pieces broken in tension parallel to the grain in the air-dried condition were examined by a scanning electron microscope to study the structural features of ruptured cell walls.

8 Résumé Wood pieces broken in tension parallel to the grain in the air-dried condition were examined by a scanning electron microscope to study the structural features of ruptured cell walls. Samples to be observed were taken both from the broken end of microtensile specimens and from the tensile side of beams broken in a bending or impact bending test. The samples were coated with carbon and gold evaporated under high vacuum. Softwood samples were mainly used in this study, while additional observations were made on hardwood ones. In the broken tracheids showing the splintering fracture type, the ruptured S2 had sharp splinters (Plate 2). In those tracheids showing the cross fracture type, the fracture crossed the wall nearly perpendicular to the tracheid axis, so that the cross fracture surface of the wall layers could be observed on the broken end of the wall. The cross fracture surface of S2 showed two characteristic features: the flat face and the ridgy face (Plate 3). The flat face was found particularly in S2 of latewood tracheids with the steep helical angles. On the flat face a granular appearance could be seen at high magnification (Plate 5), which was considered to be the broken ends of fibrils coated with carbon and gold. The impact bending test had a tendensy to increase the occurrence of the flat face fracture in latewood tracheids (Plate 8). In earlywood, however, the flat face fracture could be hardly found even in the broken tracheids showing the cross fracture type. In those tracheids the broken end of S2 had the ridgy face of the cross fracture type or the fine splinters of fibrils (Plate 7). The cross fracture surface of the intercellular layer at the cell corner appeared flat and smooth. Si was split along its fibrillar orientation. The loosened and brushy fibrils of Si were also found frequently in the split cell walls. Splitting and scission of S3 fibrils appeared to follow the break of the adjacent S2. The intercellular separation also occurred in tension, especially between latewood tracheids. Both the side face of separated tracheids and the inner face of the remainder of a wall showed the fibrillar structure of Si, indicating shear failure within Si (Plate 9). Axial and ray parenchyma cell walls of softwood broken in axial tension had the brash fractures with flat and smooth face much the same as the intercellular layer (Plate 10, 11). The smooth face of ruptured cell walls would be due to a high lignin contents in them. The vessel wall with the flat helix was split along the fibrillar orientation (Plate 12). The wall of the compression wood tracheid was split along its spiral check (Plate 13), and the gelatinous layer in tension wood fibers was severed perpendicular to its fibrils, resulting in the cross fracture with flat face (Plate 14). The fracture type of a cell wall layer by the tensile load seems to depend on the angle between the direction of the load and the fibrillar orientation of the layer. As explained in a schematic diagram Fig. 1, the tensile load with a larger angle to the fibrils of the layer would make the fibrils separate laterally, resulting in a flat helical fracture (Fig. 1d). The tensile load nearly parallel to the fibrils would cause the scission of fibrils perpendicular to them, leading to the cross fracture with the flat face. With a medium angle between the two the lateral separation and scission of fibrils would be combined in various way, resulting in transitive types of the fracture. A typical one of them is the steep helical fracture i. e. the splintering fracture (Fig. lc) and another is the cross fracture with the ridgy face (Fig. lb). It is also considered that the ridgy face may be a trace of the fracture propagation advancing the wall throughout, in which the scission of fibrils would proceed with a short, quick jump accompanying a minute split between fibrils (Fig. 2).

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~ ご再 ~ Title 經濟法令 Author(s) Citation 經濟論叢 (1925), 20(5): 925-942 Issue Date 1925-05-01 URL http://dx.doi.org/10.14989/128271 Right Type Departmental Bulletin Paper Textversion publisher Kyoto University ~ ご再

An Observation on Tensile Fracture of Wood by Scanning Electron Microscope Hiroshi SAIKI, Ikuo FURUKAWA and Hiroshi HARADA

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Title 外傷性脊髄損傷患者の泌尿器科学的研究第 3 報 : 上部尿路のレ線学的研究並びに腎機能について Author(s) 伊藤, 順勉 Citation 泌尿器科紀要 (1965), 11(4): Issue Date URL

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